Climate change and the Knysna Estuary

Abstract

Estuaries are shallow coastal environments that are influenced by both tidal action and freshwater inflow. As a result of the mixing of marine and fresh waters, estuaries are naturally dynamic, unstable environments with physico-chemical conditions oscillating on hourly, daily, seasonal, yearly and decadal scales1. Climate change is expected to modify the physical structure and biological functioning of estuaries, by changing the magnitude of these oscillations, as well as changing long-term average physico-chemical conditions (such as average temperature, salinity and dissolved oxygen levels). In addition to rising temperatures, climate change in the coastal and estuarine environment also incorporates changes in temperature variability (land and sea), winds and ocean currents, freshwater flow (rainfall), extreme weather events, sea level and ocean acidification; all of which will have profound consequences for species living in estuaries. In this chapter these different drivers of change, such as temperature, rainfall and hydrology, floods and droughts, sea level rise, storm surges and ocean acidification are reviewed with a focus on the effects of these drivers of change on the Knysna Estuary.